Display device and electronic apparatus

ABSTRACT

A display device includes a first substrate, a second substrate, and microcapsules sandwiched between the first substrate and the second substrate, the microcapsules constituting a display area, the microcapsules encapsulating a display material whose optical properties change in response to electrical stimulation. A conductive material for conducting between the substrates is provided between the first substrate and the second substrate to constitute a vertically conducting portion. The thickness of the conductive material is set such that the distance between the first substrate and the second substrate at the vertically conducting portion is larger than the distance between the first substrate and the second substrate in the display area.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. Ser. No.11/531,415 filed Sep. 13, 2006, claiming priority to Japanese PatentApplication Nos. 2005-299838 filed Oct. 14, 2005 and 2006-159799 filedJun. 8, 2006, all of which are incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a display device provided withmicrocapsules and an electronic apparatus including the display device.

2. Related Art

Hitherto, electrophoretic display devices, each of which includes anelectrophoretic dispersion liquid containing a liquid-phase dispersionmedium and electrophoretic particles and utilizes the phenomenon in thatthe distribution state of the electrophoretic particles changes in thepresence of an applied electric field, thus changing the opticalproperties of the electrophoretic dispersion liquid, have been known(for example, refer to Japanese Unexamined Patent ApplicationPublication No. 9-185087 [Patent Document 1]). In such electrophoreticdisplay devices, since a backlight is not required, the cost can bereduced and the thickness can be decreased. Moreover, theelectrophoretic display devices provide a wide angle of view and a highcontrast, and also have memory effects in terms of display. Therefore,the electrophoretic display devices have been receiving attention as anext-generation display device.

Furthermore, in a known electrophoretic display device, anelectrophoretic dispersion liquid is encapsulated in microcapsules, andthe microcapsules are sandwiched, for example, between a transparentsubstrate provided with a transparent electrode which serves as a commonelectrode and a substrate provided with pixel electrodes. Encapsulationof the electrophoretic dispersion liquid in microcapsules isadvantageous in that it is possible to prevent the dispersion liquidfrom flowing out during the fabrication process of the display device,and it is possible to decrease sedimentation and aggregation of theelectrophoretic particles.

In such an electrophoretic display device provided with microcapsules,as a method for providing conduction between the transparent electrodeand the substrate, a technique of using a conductive material includinga resin and conductive particles incorporated therein is generallyemployed. As the conductive material, a conductive paste including aresin, such as epoxy, and conductive particles, such as metal particles,e.g., silver, or carbon particles, are incorporated therein, or aconductive sheet produced by forming the conductive paste into a sheetis known.

When conduction is achieved between the substrates using such aconductive material, in order to prevent the occurrence of colorirregularity and the like, the thickness (height) of the conductivematerial is set so that the distance between the substrates in thedisplay area composed of the microcapsules is the same as the distancebetween the substrates at a vertically conducting portion which isconducted by the conductive material, and the vertically conductingportion is formed.

However, in the display device having the structure described above,when reliability tests, such as a high-temperature preservation test anda temperature cycling test, are performed, in some cases, separation mayoccur between the transparent substrate or the substrate and theconductive material due to thermal expansion and thermal shrinkage ofthe resin in the conductive material, resulting in defective continuity.When defective continuity occurs in such reliability tests, it isexpected that long-term reliability may not be ensured when the productis in the market. Therefore, it has been strongly demanded to takemeasures against the problems.

SUMMARY

An advantage of the invention is that it provides a display device inwhich occurrence of defective continuity resulting from separationbetween a substrate and a conductive material is prevented and long-termreliability is ensured, and an electronic apparatus including thedisplay device.

According to an aspect of the invention, a display device includes afirst substrate, a second substrate, and microcapsules sandwichedbetween the first substrate and the second substrate, the microcapsulesconstituting a display area, the microcapsules encapsulating a displaymaterial whose optical properties change in response to electricalstimulation, wherein a conductive material for conducting between thesubstrates is provided between the first substrate and the secondsubstrate to constitute a vertically conducting portion, and wherein thethickness of the conductive material is set such that the distancebetween the first substrate and the second substrate at the verticallyconducting portion is larger than the distance between the firstsubstrate and the second substrate in the display area.

In the display device, the thickness of the conductive material is setsuch that the distance between the first substrate and the secondsubstrate at the vertically conducting portion is larger than thedistance between the first substrate and the second substrate in thedisplay area. Thus, the first substrate and/or the second substrateare/is warped outward at the vertically conducting portion andelastically deformed with respect to the display area. Consequently, thefirst substrate and/or the second substrate, due to the resiliencethereof, exert/exerts force that acts inward, i.e., force that pressesthe conductive material side, in particular at the vertically conductingportion. Since the first substrate and/or the second substrate alwayspress/presses the conductive material side in such a manner, forexample, even if a reliability test, such as a high-temperaturepreservation test or a temperature cycling test, is performed,separation between the first substrate or the second substrate and theconductive material is prevented, and thus long-term reliability as aproduct is ensured.

In the display device, preferably, the thickness of the conductivematerial is set such that the distance between the first substrate andthe second substrate at the vertically conducting portion is larger thanthe distance between the first substrate and the second substrate in thedisplay area by a range of 10 to 200 μm. If the difference of thedistance between the substrates at the vertically conducting portion isless than 10 μm, the pressing force due to the resilience toward theconductive material is decreased, and there is a possibility thatseparation may occur in the reliability test. If the difference exceeds200 μm, there is a possibility that, because of the change with time fora long period of time, the microcapsules lying in the vicinity of thevertically conducting portion may be separated from the substrates,resulting in defective display. Consequently, by specifying the range of10 to 200 μm, both long-term reliability on defective continuity andlong-term reliability on defective display can be ensured.

Furthermore, in the display device, preferably, the verticallyconducting portion is disposed at the perimeter of each of the firstsubstrate and the second substrate. In such a manner, since theresilience acts more strongly, the force that presses the conductivematerial side is more satisfactorily exerted.

Furthermore, in the display device, preferably, an adhesive layer whichbonds the first substrate to the second substrate is provided betweenthe first substrate and the second substrate at a position differentfrom that of the vertically conducting portion and from that of thedisplay area. In such a manner, the first substrate and the secondsubstrate are bonded to each other more strongly, and thus separationbetween each substrate and the conductive material can be prevented.

Furthermore, in the display device, preferably, a substrate electrode isdisposed on one of the first substrate and the second substrate at aposition including the vertically conducting portion, and the adhesivelayer is provided on the substrate electrode excluding a position atwhich the vertically conducting portion is disposed. In such a manner,in particular bonding between the substrate electrode and the conductivematerial can be reinforced by the adhesive layer.

Furthermore, in the display device, preferably, the adhesive layer isprovided between the microcapsules and the vertically conductingportion. In such a manner, the first substrate and the second substrateare bonded to each other more strongly, and also bonding in the vicinityof the vertically conducting portion becomes stronger, thus preventingseparation of the vertically conducting portion from the first substrateor the second substrate.

Furthermore, in the display device, preferably, the microcapsules arebonded to the first substrate or the second substrate, and an adhesiveof the adhesive layer is the same as an adhesive for bonding themicrocapsules to the first substrate or the second substrate. In such amanner, the step of forming the adhesive layer can be carried outsimultaneously with the step of sandwiching the microcapsules, thusbeing advantageous in terms of the production process.

Furthermore, preferably, the microcapsules are bonded to the firstsubstrate or the second substrate with an adhesive sheet having athickness of 25 μm or more, and the adhesive of the adhesive layer isformed by a portion of the adhesive sheet protruded out toward thevertically conducting portion. By using the adhesive sheet with athickness of 25 μm or more and heating the adhesive sheet, the adhesivesheet is softened, and a portion thereof protrudes out toward thevertically conducting portion. The adhesive sheet is hardened in such astate to constitute the adhesive layer. Consequently, the adhesive layercan be formed without adding a new processing step, thus being extremelyadvantageous in terms of the production process.

Furthermore, in the display device, preferably, the adhesive layer iscomposed of a moisture-resistant resin, and the adhesive layer isdisposed outside the vertically conducting portion and the display areaso as to surround the vertically conducting portion and the displayarea. In such a manner, it is possible to prevent corrosion of theelectrode due to damp (moisture), degradation of the microcapsules, andthe like.

According to another aspect of the invention, an electronic apparatusincludes the display device described above. Since the electronicapparatus includes the display device in which long-term reliability isensured, the electronic apparatus itself has also ensured long-termreliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a sectional side elevation showing a schematic structure of adisplay device according to an embodiment of the invention.

FIG. 2 is a plan view showing an interior side of a first substrate.

FIG. 3 is a plan view showing an interior side of a first substrate.

FIGS. 4A to 4D are schematic diagrams used for describing a method forfabricating a display device step by step.

FIG. 5 is a schematic structural diagram used for describing a displaydevice according to another embodiment of the invention.

FIG. 6 is a perspective view showing an external structure of acomputer, which is an example of the electronic apparatus of theinvention.

FIG. 7 is a perspective view showing an external structure of a mobilephone, which is an example of the electronic apparatus of the invention.

FIG. 8 is a perspective view showing an external structure of a sheet ofelectronic paper, which is an example of the electronic apparatus of theinvention.

FIG. 9 is a perspective view showing an external structure of anelectronic notebook, which is an example of the electronic apparatus ofthe invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The invention will be described in detail below. FIG. 1 is a schematicdiagram showing a display device according to an embodiment of theinvention. In FIG. 1, reference numeral 1 represents a display device.Note that, in FIGS. 1 and 4A to 4D, in order to facilitate understandingof the characteristic parts of the invention, the device isschematically shown with the size and shape being extremely changed fromthe actual size and shape. In particular, although microcapsules in thecenter and microcapsules at both ends are shown to have differentdiameters, all the microcapsules are actually formed so as to havesubstantially the same diameter.

The display device 1 includes a first substrate 3 provided with aplurality of pixel electrodes 2 and a second substrate 5 provided with acommon electrode (counter electrode) 4. Microcapsules 6 encapsulating adisplay material are sandwiched between the first substrate 3 and thesecond substrate 5. Such a display device 1 can be designed so as tohave one display surface (view surface) or two display surfaces (viewsurfaces). The substrate and electrode on the display surface side musthave high light transmission properties, and in particular, arepreferably transparent. In this embodiment, as will be described below,the second substrate 5 is a transparent substrate and the commonelectrode 4 is a transparent electrode. Thus, the second substrate 5side is a display surface.

Many pixel electrodes 2 are disposed on the inner surface of the firstsubstrate 3, and also wiring formed by a copper foil pattern or the like(not shown), which is connected to the pixel electrodes 2, is disposedthereon. Furthermore, substrate electrodes 7 are disposed outside thepixel electrodes 3 at the perimeter of the first substrate 3. Thesubstrate electrodes 7 are each electrically connected to an externalpower source, for example, through a flexible printed circuit board(FPC), and electrically connected to the second substrate 5 through aconductive material 8.

As each of the first substrate 3 and the second substrate 5, arectangular, film-shaped or sheet-shaped resin substrate is used inparticular when the display device 1 is used for an IC card, electronicpaper, or the like that is required to have flexibility. Furthermore, asthe second substrate 5 which serves as a display surface (view surface)as described above, a transparent substrate (having high lighttransmission properties) is used as described above. As the material forsuch a transparent substrate (second substrate 5), for example,polyethylene terephthalate (PET), polyethersulfone (PES), orpolycarbonate (PC) is preferably used.

With respect to the first substrate 3, which does not serve as a displaysurface, since transparency (high light transmission properties) is notrequired, in addition to the materials described above, polyesters, suchas polyimide (PI) and polyethylene naphthalate (PEN), polyethylene (PE),polystyrene (PS), polypropylene (PP), polyetheretherketone (PEEK),acrylates or polyacrylates, and the like can also be used. Furthermore,when the display device is not required to have flexibility as in thecase of the general panel, glass, hard resins, and semiconductorsubstrates composed of silicon or the like can also be used.

However, in the invention, as will be described below, a structure isemployed in which at least one of the first substrate 3 and the secondsubstrate 5 is elastically deformed and resilience is exerted in thatstate, and thus at least one of the first substrate 3 and the secondsubstrate 5 must be an elastically deformable, flexible substrate. Thematerial, thickness, etc. are appropriately selected for use in order toprovide such properties.

In this embodiment, as the first substrate 3, a polyimide substrate witha thickness of 25 μm is used, and thus the first substrate 3 hasflexibility and is elastically deformable and resilient. As shown inFIG. 2, a pair of substrate electrodes 7 are disposed on the innersurface of the polyimide substrate (first substrate 3) at the perimeterof the substrate, and pixel electrodes (not shown) are disposed betweenthe substrate electrodes 7. A display area 9, which will be describedbelow, is formed corresponding to the group of pixel electrodes. Thesubstrate electrodes 7 are each composed of a copper foil pattern with athickness of 10 to 20 μm, for example, formed by a semiadditive method.

As shown in FIG. 1, the pixel electrodes 2 may be formed by a copperfoil pattern in the same step as that of forming the substrateelectrodes 7, or may be formed using a general conductive material, suchas aluminum (Al) separately from the formation of the substrateelectrodes 7. Many pixel electrodes 2 are disposed in accordance withthe predetermined pixel shape, such as a rectangular shape, that isdesigned in advance.

In this embodiment, as the second substrate 5, a transparent substratecomposed of polyethylene terephthalate (PET) with a thickness of 200 μmis used. As described above, the transparent electrode as the commonelectrode 4 is disposed on the inner surface of the transparentsubstrate (second substrate 5). The transparent electrode (commonelectrode 4) is formed over the entire inner surface of the secondsubstrate 5, and is composed of a conductive oxide, such as indium-tinoxide (ITO), an electronically conductive polymer, such as polyaniline,an ionically conductive polymer prepared by dispersing an ionicsubstance, such as NaCl, LiClO₄, or KCl, in a matrix resin, such as apolyvinyl alcohol resin or a polycarbonate resin, or the like. In thisembodiment, the transparent electrode (common electrode 4) is composedof an ITO film formed by vapor deposition or the like.

Microcapsules 6 are disposed, in particular, on the pixel electrodes 2between the first substrate 3 and the second substrate 5 having thestructures described above. Thus, the microcapsules 6 constitute thedisplay area 9 shown in FIG. 2. As described above, the microcapsules 6encapsulate a display material, and all the microcapsules 6 are formedwith substantially the same diameter. In this embodiment, the diameteris about 30 μm. The optical properties of the display materialencapsulated change in response to electrical stimulation. Specifically,the display material is mainly composed of electrophoretic particles ora liquid crystal.

As the material mainly composed of electrophoretic particles, anelectrophoretic dispersion liquid including electrophoretic particlesand a liquid-phase dispersion medium for dispersing the electrophoreticparticles is used. Examples of the liquid-phase dispersion mediuminclude water; alcohol solvents, such as methanol, ethanol, isopropanol,butanol, octanol, and methyl cellosolve; esters, such as ethyl acetateand butyl acetate; ketones, such as acetone, methyl ethyl ketone, andmethyl isobutyl ketone; aliphatic hydrocarbons, such as pentane, hexane,and octane; alicyclic hydrocarbons, such as cyclohexane andmethylcyclohexane; aromatic hydrocarbons, such as benzene, toluene,xylene, and long-chain alkyl group-containing benzenes, e.g.,hexylbenzene, heptylbenzene, octylbenzene, nonylbenzene, decylbenzene,undecylbenzene, dodecylbenzene, tridecylbenzene, and tetradecylbenzene;halogenated hydrocarbons, such as methylene chloride, chloroform, carbontetrachloride, and 1,2-dichloroethane; carboxylate salts; and varioustypes of oil. These liquid-phase dispersion media may be used alone orin combination together with a surfactant or the like.

The electrophoretic particles are organic or inorganic particles(polymer or colloid) which move by electrophoresis caused by thepotential difference in the liquid-phase dispersion medium. Examples ofthe electrophoretic particles include black pigments, such as anilineblack, carbon black, and titanium black; white pigments, such astitanium dioxide, zinc oxide, and antimony trioxide; yellow pigments,such as isoindolinone, chrome yellow, yellow iron oxide, cadmium yellow,titanium yellow, and antimony; azo pigments, such as monoazo, disazo,and polyazo; red pigments, such as quinacridone red and chromevermillion; blue pigments, such as phthalocyanine blue, indanthreneblue, anthraquinone dyes, Prussian blue, ultramarine blue, and cobaltblue; and green pigments, such as phthalocyanine green. These pigmentsmay be used alone or in combination of two or more.

Furthermore, as necessary, these pigments can be incorporated with anelectrolyte, a surfactant, a charge controlling agent composed ofparticles of a metal soap, a resin, rubber, oil, varnish, a compound, orthe like, a dispersing agent, such as a titanium coupling agent, analuminum coupling agent, or a silane coupling agent, a lubricant, astabilizer, or the like. As a material for forming the wall membrane ofthe microcapsules 6, a gum arabic-gelatin composite membrane, or acompound, such as a urethane resin or a urea resin, can be used.

In the display device 1 of this example, two types of electrophoreticparticles are encapsulated in the microcapsules 6. The particles of onetype are negatively charged, and the particles of the other type arepositively charged. As the two types of electrophoretic particles, forexample, titanium dioxide, which is a white pigment, and carbon black,which is a black pigment, are used. By using such white and blackelectrophoretic particles, for example, when numbers and the like aredisplayed, the numbers and the like can be displayed by the blackelectrophoretic particles. Alternatively, display may be performed byusing only one type of electrophoretic particles and subjecting theparticles to electrophoresis toward the common electrode 4 or the pixelelectrodes 2.

Furthermore, the microcapsules 6 are fixed, in particular, on the commonelectrode 4 of the second substrate 5 with a binder 10. As the binder10, any material that has good affinity for the wall membrane of themicrocapsule 6, excellent adhesion to the common electrode 4, andinsulating properties can be used. Examples thereof includepolyethylene, chlorinated polyethylene, ethylene-vinyl acetatecopolymers, ethylene-ethyl acrylate copolymers, polypropylene, ABSresins, methyl methacrylate resins, vinyl chloride resins, vinylchloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloridecopolymers, vinyl chloride-acrylate copolymers, vinylchloride-methacrylic acid copolymers, vinyl chloride-acrylonitrilecopolymers, ethylene-vinyl alcohol-vinyl chloride copolymers,propylene-vinyl chloride copolymers, vinylidene chloride resins, vinylacetate resins, polyvinyl alcohol, polyvinyl formal, thermoplasticresins, such as cellulosic resins, polyamide resins, polymers, such aspolyacetal, polycarbonate, polyethylene terephthalate, polybutyleneterephthalate, polyphenylene oxide, polysulfone, polyamide-imide,polyaminobis-maleimide, polyethersulfone, polyphenylene sulfone,polyarylate, grafted polyphenylene ether, polyetheretherketone, andpolyether imide, fluorocarbon resins, such as polytetrafluoroethylene,polyfluoroethylenepropylene, tetrafluoroethylene-perfluoroalkoxyethylenecopolymers, ethylene-tetrafluoroethylene copolymers, polyvinylidenefluoride, polytrifluoroethylene chloride, and fluororubber, and siliconresins, such as silicone resins and silicone rubber. Other examplesinclude methacrylic acid-styrene copolymers, polybutylene, and methylmethacrylate-butadiene-styrene copolymers.

The microcapsules 6 are fixed on the pixel electrodes 2 of the firstsubstrate 3 by a double-faced adhesive sheet 11. The double-facedadhesive sheet 11 has a thickness of about 25 μm and is composed ofrubber, an acrylic resin, or the like having adhesion. The double-facedadhesive sheet 11 is bonded to the pixel electrodes 2 of the firstsubstrate 3 and bonded to the microcapsules 6, thus holding themicrocapsules 6 on the first substrate 3. By such a structure, themicrocapsules 6 are sandwiched between the first substrate 3 and thesecond substrate 5 to constitute the display area 9.

The substrate electrodes 7 are disposed outside the display area 9 asshown in FIG. 2, and a conductive material 8 is disposed on thesubstrate electrodes 7. The conductive material 8 together with eachsubstrate electrode 7 constitutes a vertically conducting portion 12which conducts between the first substrate 3 and the second substrate 5.The conductive material 8 is composed of a resin and conductiveparticles incorporated therein. That is, the conductive material 8 iscomposed of a conductive paste prepared by mixing conductive particlesinto a resin, such as an epoxy resin, the conductive particles formed bysubjecting cores composed of metal particles, such as silver or nickelparticles formed by crushing, carbon particles, or a resin, tonickel-plating and gold-plating, or a conductive sheet produced byforming the conductive paste into a sheet. In particular, with respectto the resin, as a resin having adhesion at normal temperature, therubber or the acrylic resin used for the double-faced adhesive sheet 11is also preferably used.

Here, with respect to the thickness of the conductive material 8 which,together with the substrate electrode 7, constitutes the verticallyconducting portion 12, the thickness of the conductive material 8 is setsuch that the distance W1 between the first substrate 3 and the secondsubstrate 5 at the vertically conducting portion 12 is larger than thedistance W2 between the first substrate 3 and the second substrate 5 inthe display area. That is, the distance W1 between the first substrate 3and the second substrate 5 at the vertically conducting portion 12 issubstantially equal to the total thickness of the substrate electrode 7,the conductive material 8, and the common electrode 4, and the distanceW2 between the first substrate 3 and the second substrate 5 in thedisplay area is substantially equal to the total of the thickness of thepixel electrode 2 and the double-faced adhesive sheet 11, the thicknessof the microcapsules 6 and the binder 10, and the thickness of thecommon electrode 4. Consequently, by setting the thickness of theconductive material 8 larger than the total of the diameter of themicrocapsule 6 and the thickness of the double-faced adhesive sheet 11,the distance W1 can be set larger than the distance W2.

By setting the distance W1 between the substrates at the verticallyconducting portion 12 larger than the distance W2 between the substratesin the display area 9 in such a manner, as shown in FIG. 1, thevertically conducting portion 12 sides, i.e., outer ends, of the firstsubstrate 3, which has a particularly small thickness, are elasticallydeformed (warped) outward in a direction indicated by arrow A in FIG. 1.As a result, the first substrate 3, due to the resilience thereof,exerts force that acts inward as indicated by arrow B in FIG. 1, i.e.,force that presses the conductive material 8 side.

Here, the largeness of the distance W1 with respect to the distance W2,i.e., the difference between the distance W1 and the distance W2, ispreferably in the range of 10 to 200 μm, and particularly preferably inthe range of 50 to 80 μm. If the difference is less than 10 μm, thepressing force due to the resilience toward the conductive material 8 isdecreased, and there is a possibility that separation may occur in thereliability test. If the difference exceeds 200 μm, there is apossibility that, because of the change with time for a long period oftime, the microcapsules 6 lying in the vicinity of the verticallyconducting portion may be separated from the substrate 3(5), resultingin defective display. Consequently, by designing the thickness of theconductive material 8 such that the difference between the distance W1and the distance W2 is in the range of 10 to 200 μm, both long-termreliability on defective continuity and long-term reliability ondefective display can be ensured. In particular, by specifying the rangeof 50 to 80 μm, the long-term reliability can be more satisfactorilyensured.

There may be a case where a plurality of vertically conducting portions12 are present, and consequently, variation occurs in the distance W1between the substrates at these vertically conducting portions 12. Insuch a case, the average of a plurality of distances W1 is considered asthe distance W1 between the substrates at the vertically conductingportion 12 in the invention. As shown in FIG. 1, variation also occursin the distance W2 between the substrates in the display area 9. Withrespect to the distance W2, the minimum value of a plurality ofdistances W2 is considered as the distance W2 between the substrates inthe display area 9.

As shown in FIG. 2, the conductive material 8 constituting thevertically conducting portion 12 is not disposed over the entire surfaceof each substrate electrode 7 and is disposed on a part of the uppersurface of the substrate electrode 7. Consequently, a region in whichthe substrate electrode 7 and the conductive material 8 are stackedcorresponds to the vertically conducting portion 12 in the invention.The adhesive layer 13 is disposed on the substrate electrode 7 at aposition not provided with the conductive material 18 and in thevicinity thereof. As described above, the adhesive layer 13 is disposedat a position different from that of the vertically conducting portion12 and also from that of the display area 9. By disposing the adhesivelayer 13 between the first substrate 3 and (the common electrode 4 of)the second substrate 5, the first substrate 3 and the second substrate 5are fixed to each other and the substrates are bonded to each other morestrongly.

In particular, when the adhesive layer 13 is composed of a resin thathas stronger adhesion than that of the conductive material 8, since theadhesive layer 13 is provided on the substrate electrode 7, adhesionbetween the substrate electrode 7 and the conductive material 8 isreinforced, and separation therebetween is prevented. Furthermore, whenthe adhesive layer 13 is composed of a moisture-resistant resin, inparticular, by disposing the adhesive layer 13 in the vicinity of thesubstrate electrode 7 outside the vertically conducting portion 12 andthe display area 9 so as to surround the vertically conducting portion12 and the display area 9, it is possible to prevent corrosion of theelectrode due to damp (moisture), degradation of the microcapsules, andthe like. As the moisture-resistant resin, a resin having highcrosslinking density, such as an epoxy resin, is used.

In FIG. 2, the conductive material 8 is disposed on the substrateelectrode 7 at one position, and one vertically conducting portion 12 isformed on one substrate electrode 7. However, as shown in FIG. 3, theconductive material 8 may be disposed on the substrate electrode 7 at aplurality of (e.g., three) positions, and a plurality of verticallyconducting portions 12 may be formed on one substrate electrode 7. Insuch a case, by disposing the adhesive layer 13 between the plurality ofportions of the conductive material 8, as described above, bondingbetween the substrate electrode 7 and the conductive material 8 can bereinforced, and separation therebetween can be prevented.

In order to fabricate a display device 1 having the structure describedabove, first, as shown in FIG. 4A, a first substrate 3 composed of anelastically deformable polyimide with a thickness of about 25 μm isprepared, and substrate electrodes 7 and pixel electrodes 2 are formedthereon by a known method, such as the semiadditive method.Subsequently, as shown in FIG. 4B, the conductive sheet described above,as a conductive material 8, is disposed at a predetermined position ofeach substrate electrode 7 and bonded thereto. The thickness of theconductive sheet, serving as the conductive material 8, is set as apredetermined thickness such that the distance W1 is larger than thedistance W2 in FIG. 1 as described above.

Furthermore, separately, as a second substrate 5, a transparentsubstrate composed of polyethylene terephthalate (PET) is prepared, anda transparent electrode (common electrode 4) composed of ITO is formedover one surface (inner surface) thereof by vapor deposition or thelike. Then, many microcapsules 6 are bonded to a predetermined positionon the common electrode 4 of the second substrate 5, i.e., the positioncorresponding to the display area 9, using a binder 10. Subsequently, adouble-faced adhesive sheet 11 is bonded to a side opposite to thesecond substrate 5 side of the microcapsules 6.

Subsequently, the second substrate 5 to which the double-faced adhesivesheet 11 has been thus bonded is disposed on the first substrate 3 so asto face the first substrate 3. Then, as shown in FIG. 4C, thedouble-faced adhesive sheet 11 of the second substrate 5 is pressedagainst the surface of the first substrate 3 provided with the pixelelectrodes 2 and the double-faced adhesive sheet 11 is bonded thereto.Simultaneously, the common electrode 4 of the second substrate 5 ispressed against the conductive material 8 on the first substrate 3, andbonding therebetween is performed. Thus, the first substrate 3 and thesecond substrate 5 are integrated with the conductive material 8, thedouble-faced adhesive sheet 11, and the like therebetween, and themicrocapsules 6 are sandwiched between the first substrate 3 and thesecond substrate 5. Note that bonding of the double-faced adhesive sheet11 and fixing by the conductive material 8 are basically performed atnormal temperature without heating, and as necessary, heating isperformed within a range that does not adversely affect themicrocapsules 6.

By integrating the first substrate 3 and the second substrate 5 in sucha manner, the distance W1 between the first substrate 3 and the secondsubstrate 5 at the vertically conducting portion 12 becomes larger thanthe distance W2 between the first substrate 3 and the second substrate 5in the display area 9. As a result, as shown in FIG. 4C, the perimeterof the first substrate 3 is elastically deformed (warped) outward, andresilience acts in a direction opposite to the direction of elasticdeformation.

Subsequently, an adhesive is injected into the space between the firstsubstrate 3 and the second substrate 5 from the perimeter side with adispenser or the like to dispose the adhesive at a portion in which theconductive material 8 is not disposed on the substrate electrode 7 andits vicinity, i.e., as shown in FIG. 4D, at a position surrounding theconductive portion 12 and the display area 9. Then, by curing theadhesive, an adhesive layer 13 is formed, and a display device 1 isthereby obtained. As the adhesive, a UV-curing type adhesive or the likethat is cured without heating is used. However, as in the bondingtreatment of the double-faced adhesive sheet 11 or the like, it is alsopossible to use an adhesive that is cured by heating within a range thatdoes not adversely affect the microcapsules 6.

In the display device 1 thus obtained, the vertically conducting portion12 is formed by setting the thickness of the conductive material 8 suchthat the distance W1 between the substrates at the vertically conductingportion 12 is larger than the distance between the substrates in thedisplay area 9. Thus, as described above, the first substrate 3, due tothe resilience thereof, exerts force that presses the conductivematerial 18 side as indicated by arrow B in FIG. 1 in particular, at thevertically conducting portion 12. Since the first substrate 3 pressesthe conductive material 8 side in such a manner, for example, even if areliability test, such as a high-temperature preservation test or atemperature cycling test, is performed, separation between the firstsubstrate 3 or the second substrate 5 and the conductive material 8 isprevented, and thus long-term reliability as a product is ensured.

The invention is not limited to the embodiment described above. It is tobe understood that various alterations may be made to the embodimentwithout departing from the spirit and scope of the invention. Forexample, in the fabrication process of the display device 1, when thedouble-faced adhesive sheet 11 is bonded to a side of the microcapsules6 bonded to the second substrate 5 opposite to the second substrate 5side, as the double-faced adhesive sheet 11, a double-faced adhesivesheet having a thickness of 25 μm or more may be used. When such adouble-faced adhesive sheet 11 is used and the double-faced adhesivesheet 11 is pressed against the surface of the first substrate 3provided with the pixel electrodes 2 for bonding and fixing, forexample, by heating at a temperature of 50° C. or higher (thetemperature within a range that does not adversely affect themicrocapsules 6), the double-faced adhesive sheet 11 is softened and apart thereof is allowed to protrude out toward the vertically conductingportion 12. Subsequently, curing is performed in that state. Thus, theportion allowed to protrude out between the microcapsules 6 and thevertically conducting portion 12 is used as an adhesive layer 14 asshown in FIG. 5.

Subsequently, as in the case shown in FIG. 4D, an adhesive is injectedinto the space between the first substrate 3 and the second substrate 5from the perimeter side with a dispenser or the like, and the adhesiveis cured to form an adhesive layer 13. Thereby, a display device isobtained.

In such a display device, the same advantageous effect as that in thedisplay device 1 is obtained. In addition, bonding between the firstsubstrate 3 and the second substrate 5 is stronger, and bonding in thevicinity of the vertically conducting portion 12 is stronger. Thus,separation of the vertically conducting portion 12 from the firstsubstrate 3 or the second substrate 5 can be reliably prevented.Furthermore, since the adhesive layer 14 is formed using thedouble-faced adhesive sheet 11 simultaneously with the step ofsandwiching the microcapsules between the first substrate 3 and thesecond substrate 5, the adhesive layer 14 can be formed without anadditional step, thus facilitating the fabrication process.

Furthermore, in the embodiment described above, the first substrate 3provided with the pixel electrodes 2 is elastically deformed outward bysetting the thickness of the first substrate 3 smaller than that of thesecond substrate 5 provided with the common electrode 4 or the like.However, the second substrate 5 may be designed to be resilient.Alternatively, by designing the first substrate 3 and the secondsubstrate 5 so as to have the same strength, both substrates may beelastically deformed to allow each substrate to exert resilience.Furthermore, in the embodiment, a case in which one display area ispresent has been described. The invention is also applicable to a casein which a plurality of display areas are each independently formed likean island.

Electronic apparatuses according to some embodiments of the inventionwill now be described below. The electronic apparatuses according to theembodiments of the invention each include the display device accordingto the embodiment of the invention described above. Examples of theelectronic apparatus including the display device will be describedbelow.

Mobile Computer

First, an example in which the display device is applied to a mobilepersonal computer will be described. FIG. 6 is a perspective viewshowing a structure of the personal computer. As shown in FIG. 6, apersonal computer 80 includes a main body 82 provided with a keyboard 81and a display unit provided with the display device 64.

Mobile Phone

Next, an example in which the display device is applied to a display ofa mobile phone will be described. FIG. 7 is a perspective view showing astructure of the mobile phone. As shown in FIG. 7, a mobile phone 90includes a plurality of operation buttons 91, an earpiece 92, amouthpiece 93, and the display device 64.

Electronic Paper

Next, an example in which the display device is applied to a display ofelectronic paper will be described. FIG. 8 is a perspective view showinga structure of the electronic paper. Electronic paper 110 includes amain body 111 composed of a rewritable sheet having texture like paperand flexibility and a display unit provided with the display device 64.

Electronic Notebook

FIG. 9 is a perspective view showing a structure of an electronicnotebook. As shown in FIG. 9, an electronic notebook 120 includes aplurality of sheets of electronic paper 110 shown in FIG. 8, which arebundled together and covered with a cover 121. By providing a displaydata input unit on the cover 121, the display content of the electronicpaper can be changed in the bundled state.

According to the electronic apparatuses described above, since thedisplay device in which long-term reliability is ensured is provided,the electronic apparatuses each itself have also ensured long-termreliability.

Examples of the electronic apparatus include, in addition to thepersonal computer shown in FIG. 6, the mobile phone shown in FIG. 7, theelectronic paper shown in FIG. 8, and the electronic notebook shown inFIG. 9, IC cards each including a display provided with the displaydevice, a fingerprint detection sensor, and the like, electronic books,viewfinder type or monitor-direct-view type video tape recorders, carnavigation systems, pagers, electronic pocket diaries, desktopelectronic calculators, word processors, workstations, televisiontelephones, POS terminals, and apparatuses provided with touch panels.Of course, the display device can be used as a display for each of thevarious types of electronic apparatuses.

1. A display device comprising: a first substrate; a second substrate; afirst adhesive layer disposed on the first substrate; microcapsulesdisposed between the first adhesive layer and the second substrate, themicrocapsules constituting a display area, the microcapsulesencapsulating electrophoretic particles; a conductive material forconducting between the substrates that is disposed between the firstsubstrate and the second substrate to constitute a vertically conductingportion, the conductive material being disposed at a position differentfrom that of the microcapsules and from that of the first adhesivelayer; and a second adhesive layer which bonds the first substrate tothe second substrate, a second adhesive layer being provided between thefirst substrate and the second substrate, the second adhesive layerbeing disposed outside the vertically conducting portion and the displayarea so as to surround the vertically conducting portion and the displayarea, wherein the thickness of the conductive material is larger thanthe total of the thickness of the microcapsule and the thickness of thefirst adhesive layer in the display area.
 2. The display deviceaccording to claim 1, wherein the thickness of the conductive materialis larger than the total of the thickness of the microcapsule and thethickness of the adhesive sheet in the display area by a range of 10 to200 μm.
 3. The display device according to claim 1, wherein the secondadhesive layer is composed of a moisture-resistant resin.
 4. Anelectronic apparatus comprising the display device according to claim 1.